Electromagnetically operated switch having a movable contact carrier shock absorber



Dec. 22, 1970 J. E. STALLMAN 355,048

' ELECTROMAGNETICALLY OPERATED SWITCH HAVING A MOVABLE CONTACT CARRIERSHOCK ABSORBER Filed July 23, 1969 FIGJ n2 114 Q 3Q 28 I68 3 9. 96 4a 964s- 4s 96 Z5 86 57 57 79 I60 |?62 92 5 92 92 |66 [NV/LV'HHQ.

94 52 JAMES E. STALLMAN United States Patent 0 3,550,048ELECTROMAGNETICALLY OPERATED SWITCH HAVING A MOVABLE CONTACT CARRIERSHOCK ABSORBER James E. Stallman, White-fish Bay, Wis., assignor toSquare D Company, Park Ridge, Ill., a corporation of Michigan Filed July23, 1969, Ser. No. 843,994 Int. Cl. H01h 3/60 US. Cl. 335-193 10 ClaimsABSTRACT OF THE DISCLOSURE An electromagnetically operated switch havingshock absorbers for reducing the bounce of the movable contacts when thecontacts are moved to a circuit closing position by a movable contactcarrier. The shock absorbing function is provided by a pair ofelastomeric members, such as butyl rubber, which are positioned on themovable contact carrier to be compressed and absorb the rebound energyof the movable contact carrier when the movable contact carrierovershoots the normal contact closing position and to be relaxed whenthe movable contact carrier is at the contact closing position.

The present invention relates to switching devices, and moreparticularly, to a structure which will absorb the rebound energy of amovable contact carrier in an electromagnetically operated switch.

The contact structure of the type with which the present invention isconcerned is particularly suited for use in electromagnetic switchingdevices commonly known as contactors, which are furnished as devices ofvarying sizes having ratings in accordance with the standardspromulgated by the National Electrical Manufacturers Association,commonly known as NEMA. An example of a contactor construction which isparticularly suited to control electrical loads of 50 amperes or less,which corresponds to a NEMA Size 2 device is disclosed in United StatesPat. No. 3,354,415, which was granted to the inventors Joseph I.Gribble, Kenneth J. Marion and Harold E. Whiting.

While the proportions of the device shown in the Gribble et al. patentmay be increased to control amperes greater than 50 amperes, economicand physical size limitations dictate that additional features should beincorporated therein if currents having a magnitude two or three times50 amperes are to be controlled by the device. It is well known that anyconductor is heated by the current passing therethrough and therefore itfollows that an increase in the current controlling capability of adevice requires a corresponding increase in the cross sectional mass ofthe current carrying metal parts of the device. Inherently, anyelectrical switch which relies on an abutting engagement between twometal parts to complete an electric circuit will operate with aphenomenon known as contact bounce, which is generated when the movablecontacts initially are in effect slammed into enagagment with thestationary contacts. Contact bounce is a well-known cause of wear, andthus is objectionable. One possible solution which may be used to reducecontact bounce is to employ extremely strong springs in the movablecontact structure. However, this solution is impractical for a number ofreasons, including the necessity of requiring an operating magnetstructure which would have to be excessively large in physical size. Thepresence of contact bounce is particularly objectionable in switches oflarger sizes and becomes more difficult to control because of the weightof the movable contacts which is required to enable the switch tocontrol the large Patented Dec. 22, 1970 "ice currents. As any conductoris heated by the current passing therethrough, common practices whichhave been heretofore followed dictated that each current carrying partin a switch be designed to operate independently of the remainingcomponents in the switch and act as its own radiator for the heatgenerated therein. However, in any electric switch, the componentscarrying current must be in firm physical contact with each other, ifoverheating of the switch is to be avoided. In the contact structure asused in the switch as will be hereinafter described, the stationarycontact structures, which have a large mass in relation to the currentpassing therethrough, are engaged by the movable contact which has asmall mass in relation to the current passing therethrough so that theheat generated within the movable contact will be conducted anddissipated by the stationary contact structures.

This philosophy of design is incorporated into a movable contactstructure disclosed in an application for US. patent, Ser. No. 844,151,which has been filed by the inventor Merlin Y. Turnbull concurrentlyherewith. An additional contributing cause of contact bounce is providedby the rebounding of the armature and the movable contact carrier whenthe carrier moves the movable contacts into engagement with thestationary contacts. It is to be appreciated during the movement of themovable contacts into engagement with the stationary contact, themovable contact carrier will overshoot its energized position andthereby over-compress the spring supports for the movable contacts. Thusthe over-compressed contact springs will supply a force which will tendto drive the movable contact carrier to a contact opening position andcause the contact carrier to oscillate about the energized position andcontribute to the bouncing of the movable contacts on the stationarycontacts. The present invention is concerned with a shock absorberarrangement which will reduce the oscillation of the movable contactcarrier when the carrier in initially moved to the energized position.

It is an object of the present invention to provide a movable contactstructure which will operate with a low degree of contact bounce and canbe readily serviced.

Another object is to provide an electromagnetically operated switch withshock absorbers that will reduce the oscillation of the carrier aboutits energized position when the carrier initially moves to its energizedposition and more specifically, to position a pair of elastomeric shockabsorbers on the carrier so the shock absorbers will be compressed whenthe carrier moves beyond its energized position and are relaxed when thecarrier is in its energized position.

A further object is to provide an electric switch with a movable contactstructure that includes a contact carrier having a portion movable in aslot in an insulating base and portions extending through openings inthe base to the front surface of the base to provide a surface on thecarrier whereon the movable contact is positioned, and to connect themovable contact to the contact carrier by a spring biased rotatableplunger that acts as an air piston to reduce the contact bounce when thecarrier moves to an energized position wherein the movable contactsfirmly engage the stationary contacts that are mounted on the frontsurface of the base and to position a pair of elastomeric shockabsorbers on the carrier so the shock absorbers will be compressed whenthe carrier moves beyond the energized position and are relaxed when thecarrier is at the energized position to thereby reduce the oscillationof the carrier when the carrier is initially moved to the energizedposition.

Further objects and features of the invention will be readily apparentto those skilled in the art from the specification and appended drawingillustrating a preferred embodiment in which:

FIG. 1 is a side view, partly in cross section, of an electric switchincorporating a shock absorber for a movable contact carrier accordingto the present invention.

FIG. 2 is a view partly in cross section taken along line 2-2 in FIG. 1.

Referring to the drawing, and particularly to FIG. 1, there is shown anelectromagnetic switch assembly 20 having a plurality of components thatare stacked one upon the other. The components of the assembly include ametal mounting plate 22, an insulating sheet-like member 24, aninsulating base 26, an insulation barrier 28, a metal housing 30, and acover 32, each of which is dis closed and described in an applicationfor United States patent, Ser. No. 844,148, which was filed by theinventor Merlin Y. Turnbull, concurrently herewith.

The metal mounting plate 22 is formed of a stamped metal part andprovides a means to secure the switch assembly 20 to a vertical paneland the like, not shown. When the plate 22 is secured to a panel, anedge 34 becomes a bottom edge of the plate 22 and a surface 36 the frontsurface of the plate 22. The plate 22 has a pair of rearwardly extendingindentations 38 along its bottom edge 34 providing a pair of spacedmounting feet having openings therein. The plate 22 also has anindentation 40 extending across its top edge which provides an elongatedmounting foot having an opening, not shown, therein. The mounting feet38 and 40 with the openings therein are provided for the purpose ofsecuring the plate 22 to a vertical panel. The plate 22 also includes anindentation 42 which extends from the bottom edge 34 rearwardly in thefront surface 36 to the indentation 40. The indentation 42 is providedto permit passage of control wires, not shown, from the upper to thelower ends of the switch 20 in the space provided by the indentation.The control wires may be connected in circuit with the switchingcontacts of a device known as an overload relay in a manner well knownto those skilled in the art. The plate 22 also is provided with suitablylocated threaded openings which act as mounting holes which are used tosecure the insulating sheetlike member 24 and base 26 to the plate 22.

The sheet 24 is preferably formed as a molded insulating part having arelatively thin cross section having a fiat rear surface engaging thefront surface 36 to cover a central portion of the indentation 42 so asto act as a cover for the wire trough. The sheet 24 is provided with apair of circular ribs 44 which are raised on the front surface of thesheet 24 on opposite sides of a vertical center of the plate 22. Theribs 44 act as seats for a pair of springs 46, as will be laterdescribed.

As disclosed in the application for United States Pat., Ser. No.844,148, supra, the base 26 and the barrier 28 are formed of a moldedinsulating material having arc suppresing capabilities and cooperatewith each other to provide a cavity which is divided into threecompartments 48, having equal widths. The base 26 has a rear surface 50positioned on the insulating sheet 24 and the plate 22 in a securedposition by suitable screws which pass through openings in the base 26and the sheet 24 and are threadedly received in the housing holes in theplate 22. Extending into the material of the base 26 forwardly of therear surface 50 and through the side walls of the base 26 is a slot 52.The slot 52 is centered on a center-line equidistant between a top wall54 and a bottom wall 56 of the base 26 and is exposed to each of thecompartments 48 by an opening 57. The compartments 48 each extendbetween the top wall 54 and the bottom wall 56 and each have a pair ofterminal and stationary contact assemblies secured therein.

The terminal and stationary contact assemblies in each of thecompartments 48 are arranged so that the contact assemblies of each pairare spaced equidistantly on opposite sides of the slot 52 and face inopposite directions. Each of the contact assemblies includes a terminalmember 58 and a contact member 60. When the pairs of terminal andcontact assemblies are secured at the opposite ends of the compartments48, the terminal members 58 will have a wire connecting portion 62extending external of the top wall 54 and the bottom wall '56 and thecontact members 60 will have an inclined stationary contact surface 64positioned on opposite sides of the slot 52.

As disclosed in an application for United States patent, Ser. No.844,148, supra, the barrier 28, the metal housing 30 and cover 32 definean internal closed cavity 66 wherein an electromagnet 68 is included.The electromagnet 68 operates a bell crank lever 70 which has a pair ofarms 72 connected to a movable U-shaped contact carrier 74. The U-shapedcontact carrier 74 has a bight portion 76 which is movable forwardly andrearwardly in the slot 52. The movable contact carrier 74, including thebight portion 76, is most clearly disclosed in an application for UnitedStates patent, Ser. No. 844,100, concurrently filed herewith which hasbeen assigned by the inventors Merlin Y. Turnbull and Harold E. Whitingto the assignee of the present invention. The barrier 28 has a bodyportion 78 which provides a front wall for the compartments 48 andsuitable ribs 79 which provide side walls for the compartments.Extending from the body portion 78 are ears 80 that are arranged to seatupon the forward ends of a pair of posts 82 at the top and bottom walls54 and 56. The posts 82 each has a threaded insert molded therein andeach of the ears 80 has an opening therein which permits the barrier 28to be removably secured to the front surface of the base 26 by screws 84which pass through the openings in the ears 80 into the threaded insertsin the posts 82. It is readily apparent that the removal of the screws84 'will permit the assembly including the barrier 28, the housing 30and the cover 32 to be detached from the base 26 to permit access to thestationary and the movable contacts within the compartments 48 in eventthe contacts require inspection or replacement.

The movable contact carrier 74 is preferably formed as a U-shaped moldedpart that includes the bight portion 76. The bight portion 76 isreceived in the slot 52 while arms 86, which extends from opposite endsof the bight portion 76, extend externally of the side walls of the base26 have free ends received in channels in the housing 30 defined byportions on the housing 30. The free ends of the arms 86 each receive abearing 88 on a terminal end on an arm 72 of the bell crank lever 70.Extending forwardly of the bight portion 76 are a plurality of spacedprojections 92 each of which extends into one of the compartments 48.The bight portion 76 has a rear surface 94 and each of the projections92 has a front surface whereon a movable contact assembly 96 ispositioned, in a manner disclosed in an application for United Statespatent, Ser. No. 844,151, which has been filed by the inventor Merlin Y.Turnbull concurrently herewith.

Each of the movable contact assemblies 96 includes a U-shapedchannel-like member 97 having a central portion 98 positioned adjacentthe front surface of the projections 92 and a pair of portions 99extending at an angle from opposite ends of the central portion whereona pair of contact members providing contact surfaces 100 are secured.The angle of incline of the portions 99 corresponds to the angle ofincline of the stationary contact surfaces 64 so the contact surfaces100 will properly engage the contact surfaces 64. The central portion 98has an opening therein which receives a stern 101 portion on a plunger102. The free end of the stern portion 101 has a pin 103 extendingtherethrough which maintains the member 97 assembled on the free end ofthe plunger 102. The stem portion 101 of the plunger 102 extends throughan opening in the front surface of the projection 92 to a cylindricalportion 104 which is guided and movable in a cylindrical bore 105 in theprojection 92. The pin 103 is held in tight engagement with a forwardsurface of the central portion 98 by a spring 106 which surrounds thestem portion 101 and has its opposite ends resting on the cylindricalportion 104 and a spring seat at the end of the bore 105 that isadjacent the front surface of the projections 92. If desired, thecylindrical portion 104 may be provided with an annular groove whichreceives an O-ring seal 107 which will improve the air piston-likeaction of the cylindrical portion 104 in the bore 105 when the contactsurfaces 100 engage the contact surfaces 64.

The housing preferably is formed as a cast metal part which has a highthermal conductivity. While aluminum may be used to form the housing 30in that it possesses high thermal conductivity and is light weight,because of its resistance to impact, the housing part 30 is preferablyformed of a Zinc die cast material to have a bottom wall 108, a top wall110 and a pair of side walls 112 and 114 which has a rear edge 115resting on a front surface of the barrier 28 and an open front wall 116which is closed by the cover 32. The front surface of the barrier 28 andthe walls 108, 110, 112 and 114 define the cavity 66 which has a frontside closed by the cover 32. The cover 32, when removed, provides accessto the electromagnet 68 that is positioned within the cavity 66 forinspection and for service purposes. Extending inwardly from the wallsof the housing 30 are suitably located ledges each having an openingtherein which are arranged to engage portions of the front surface ofthe barrier 28 which receive screws that are threaded into suitablylocated threaded inserts that are embedded in the barrier 28 to securethe housing 30 to the barrier 28. Additionally extending inwardly alongthe rear edge 115 from the top wall 110 at the intersection of the sidewalls 112 and 114 are a pair of ledges 118 each of which has a rearsurface resting on the front surface of the barrier 28 and has a frontsurface whereon a pair of spring biased supports 120 are secured. Thespring biased supports are identical and are fully disclosed in anapplication for United States patent, Ser. No. 844,029, which has beenfiled by the inventors Harold E. Whiting and Merlin Y. Turnbullconcurrently herewith. Each of the supports 120 includes a supportportion 122, a slider 124 and a spring 126. As shown in FIG. 1, securedto a rear surface of the cover are a pair of spring biased supports 128which are identical and face in opposite directions to the spring biasedsupports 120.

The electromagnet 68, which is positioned within the cavity 66, includesa magnet coil 130, an armature 132 and a magnet core 134. The magnetcoil 130 is positioned by portions of the cover 32 and the front surfaceof the barrier 28 so that a centrally located opening through the coil100 extends along an axis perpendicular to the top and the bottom walls110 and 108. The armature 132 includes a laminated stack 136 of T-shapedlaminated magnet iron pieces and a member 138. The member 138 has a pairof arm portions secured on opposite sides of the laminated stack 136 byrivets which secure the laminated stack 136 and the arm portions of themember 138 together and a portion 140 which is generally U-shaped andbox-like and provides a connection with an end portion of an operatingarm 142 on the bell crank lever 70 in a manner described in theapplication for United States patent, Ser. No. 844,100, supra.

The magnet core 134 includes a laminated stack of E- shaped laminatedmagnet iron pieces designated by a numeral 144 and a pair of members 146and 148. The members 146 and 148 are secured on opposite sides of thelaminated stack 144 by rivets which secure the laminations of the stack144 and the members 146 and 148 together. The laminated stack 144 has anupper wall 150, a pair of pole faces 152 facing downwardly on the outerlegs of the E-shaped pieces. The upper wall 150 is substantially flatand extends substantially over the entire upper end of the E-shapedstack of laminated pieces. The

members 146 and 148 each have a pair of identical ears 154 formedthereon. Each of the ears 154 extends perpendicular to the main bodyportion of the respective members 146 and 148 so as to present a surface156 that is displaced a slight distance downwardly of the upper wall 150and a surface that faces in the same direction as the pole faces 152.Further, each of the ears 154 is provided with a notch, not shown, thatextends from a free end of the ears 154 toward the laminated stack 144.

Extending forwardly in the rear surface 94 of the movable contactcarrier 74 are a pair of circular recesses 158 which provide seats forone end of the pair of springs 46 that have their opposite endspositioned by the circular ribs 44. Also extending forwardly in the rearsurface 94 adjacent the outer ends of the bight portion 76 are a pair ofcircular recesses 160, each of which receives one of a pair of shockabsorbers 162. The stock absorbers are cylindrical and have a circularbore 164 extending therethrough. The shock absorbers 162 are tightlyreceived within the recesses 160 so as to be held assembled with thecontact carrier 74 and have a portion 166 extending a predetermineddistance from the rear surface 94 so as to engage the front surface 36when the carrier 74 initially causes the contact surfaces 64 and toengage each other as will be described.

The mounting plate 22, the insulating member 24, the base 26, thestationary contacts assemblies, the movable contact carrier 74 with themovable contact assemblies 96 thereon, the barrier 28, the housing 30and the bell crank lever 70 which is positioned within the cavity 66 areall assembled in a manner disclosed in the application for United Statespatent, Ser. No. 844,148, supra. After the foregoing mentioned parts areassembled, the electromagnet 68 is installed in the cavity 66 byassembling the armature 132, coil 130 and the magnet core 134 in thecavity 66 and securing the cover 32 to the housing 30 as disclosed inthe application for United States patent, Ser.

No. 844,034, supra.

The operation of the switching device 20 is as follows. While the switch20 will operate when mounted on a horizontal support, it is particularlysuited to be mounted on a vertical panel, not shown, so that thearmature 132 will be moved by the combined forces furnished by gravityand the springs 46 to a position whereat the pole faces of the armature132 are separated from the pole faces 152 of the magnet core 134. Theenergization of the coil 130 causes a mutual magnetic attraction to begenerated between the armature 132 and the magnet core 134. The armature132 is connected to the rotatable bell crank lever 70. The upper wall150 of the magnet core 134 is resiliently maintained in engagement withthe top wall by the spring biased supports and 128 that are respectivelycarried by the housing 30 and the cover 32. It is well known that themagnetic attraction between the armature 132 and the magnet core 134increases exponentially with the decrease in the distance between thepole faces of the armature 132 and the magnet core 134 and is at amaximum when the pole faces engage each other. The magnetic attractionbetween the armature 132 and the magnet core 134 causes the armature 132to move upwardly toward the magnet core 134 and the bell crank lever 70to rotate about its pivot. The rotating bell crank lever 70 causes themovable contact carrier 74 to move toward the plate 22 to a positionwherein the surfaces 100 on the movable contact assemblies 96 engage thecontact surfaces 64. The initial movement of the contact carrier 74 isopposed by the force of gravity on the armature 132 and by the springs46. The subsequent movement of the contact carrier 74, which occursafter the movable contacts surfaces 100 engage the contact surfaces 64,is opposed by the force of gravity on the armature 132 and the springs46 as well as the springs 106 which are associated with the movablecontact assemblies 96. Thus the resistance to the movement of thearmature 132 toward the magnet core 134 progressively increases as thesprings 46 are compressed and markedly increases as the force requiredto compress the springs 106 is added to the force required to compressthe springs 46. The magnet core 134 is exclusively supported in thecavity 66 by the spring biased supports 120 and 128 to have its upperwall 150 tightly pressed against the top wall 110 when the springs 46and 106 are fully compressed. Thus the heat generated within theelectromagnet 68 when the coil 130 is energized will be readilytransmitted to the metal housing so the metal housing may serve as aheat sink and dissipate the heat energy generated within theelectromagnet 68. However, the springs 126 biasing the supports 120 and128 are selected to provide a force which will permit the magnet core134 to move in the direction of the armature 132 in response to themutual flux between the armature 132 and the magnet core 134 just priorto the engagement between the pole faces on the magnet core 134 and thepole faces on the armature 132. Thus at the instant of impact thearmature 132 and the magnet core 134 will :be moving in oppositedirections with the magnet core 134 reversing its direction of movementand moving with the armature 132 after the impact has occurred betweenthe armature 132 and the magnet core 134. While the causes therefore arenot completely understood, it has been found that resilientlysupporting, rather than rigidly supporting, the magnet core 134 on thehousing 30 reduces the noise generated and the shock imparted to thehousing 30 which accompanies the impact between the armature 132 and themagnet core 134. Further, it has been found that the resilient supportfor the magnet core 134 reduces the shock imparted to the housing 30when the electromagnet 68 is de-energized and the armature 132 isreturned to its dropped-out position by the combined force provided bygravity and the springs 46, as well as the springs 106.

The switch 20 is shown in the de-energized position in FIG. 1. Themovement of the armature 132, as caused by the energization of theelectromagnet 68, causes the bell crank lever 70 to rotate in aclockwise direction and the contact carrier 74 to move from a retractedposition as shown toward the mounting plate 22 to an operative position.Initially the movement of the carrier 74 is opposed by the compressionof the springs 46 as the bight portion 76 moves in the slot 52 towardthe mounting plate 22. A continued movement of the carrier 74 toward theplate 22, which occurs after the contact surfaces 100 engage contactsurfaces 64, causes the central portion 98 to move out of its engagementwith the front surface of the projections 92 along a path guided by apair of spaced walls 168 that extend from the front surface of theprojections 92. The movement of the central portion 98, because of theconnection provided by the pin 103, causes the cylindrical portion 104of the plunger 102 to move in the bore 105 and the springs 106 to becompressed. When the electromagnet 68 is energized for a period of timesufficient to permit the armature 132 to be at its energized positionand the movable contact carrier 74 to be at its operative position, thesprings 106 will be compressed and have a predetermined length so as toapply a predetermined pressure between the contact surfaces 64 and 100.However, neither the armature 132 or the movable contact carrier 74 willmove directly to their energized and operative positions because of themomentum which is stored therein during their movement. It will be seenthat the moving contact carrier 74 together with the movable assemblies96 provide a considerable mass which is moving rapidly toward themounting plate 22 at an appreciable velocity. The intial engagementbetween the contact surfaces 64 and 100 will be in a direction whichwill tend to cause the contact surfaces 64 and 100 to separate with arebound action. The rebounding of the contact surfaces 100 and 64 isopposed by the operation of the cylindrical portion 104 in the bore 105which acts as an air cylinder shock absorber in a manner described inthe application for United States patent, Ser. No. 844,151, supra.

The momentum of the contact carrier 74 will cause the carrier 74 tocontinue to move toward the plate beyond the operative position so thatthe springs 46 and 106 will be compressed to have a length shorter thanthe length which they have when the carrier 74 is at the operativeposition. The excess compression of the springs 46 and 106 thus supply aforce which will tend to cause the carrier 74 to move in a directionwhich would cause the contact surfaces 64 and to separate with a contactbouncing action. The shock absorbers 162 are located on the rear surface94 to be uncompressed or relaxed when the carrier 74 is at the operativeposition; that is, when the springs 46 and 106 are compressed to have apredetermined length. The shock absorbers 162 are formed of anelastomeric material, such as butyl rubber (isobutylene-isoprene) whichhas a poor resilience or rebound characteristic at normal ambient andoperating temperatures of the switch 20 and are positioned on the rearsurface 94 to engage the plate 22 and be progressively compressed as thecarrier 74 progressively moves beyond its operative position in thedirection of the plate 22. The shock absorbers 162 have a bore 164extending therethrough. Thus as the carrier 74 moves beyond itsoperative position toward the plate 22, the shock absorbers 162 will becompressed throughout their entire length and absorb the force createdby the momentum of the carrier 74 and reduce the rebound of the carrier74 to a minimum and thereby reduce the bounce between the contactsurfaces 64 and 100.

While certain preferred embodiments of the invention have beenspecifically disclosed, it is understood that the invention is notlimited thereto, as many variations will be readily apparent to thoseskilled in the art and the invention is to be given its broadestpossible interpretation within the terms of the following claims.

What is claimed is:

1. In an electromagnetically operated switch, the combinationcomprising: a mounting plate, an insulating base secured to the mountingplate, said base providing a row of compartments that are electricallyisolated from each other, a slot in a rear Wall of the base extendingtransversely of the row of compartments along a center line of the base,said slot having a rear side closed by the mounting plate and providingan individual entry into each of the compartments through an opening inthe rear wall of each of the compartments, a pair of stationary contactsin each of said compartments with the contacts of each pair disposed inspaced relation on opposite sides of the opening, a housing mounted on afront surface of the base providing a closed cavity on a front wall ofthe base, an electromagnet assembly and a bell crank lever positionedwithin the cavity, said electromagnet having an armature movable in alinear path parallel to the rear wall of the base from a de-energizedposition to an energized position in the cavity when the electromagnetis energized, said bell crank lever having an actuating arm portionmovable by the armature and a pair of spaced arms having a free endmovable in a path toward the base during the movement of the armaturetoward the energized position, a U-shaped movable contact carrier havinga bight portion movable in the slot along a path that is perpendicularto the rear wall of the base and a pair of arms connected to the freeends of the pair of arms of the bell crank lever to move the bightportion in a direction toward the mounting plate to a contact closingposition during the movement of the armature toward the energizedposition, said bight portion having a rear surface facing and spacedfrom the mounting plate and portions on a front surface extendingthrough the openings in the base to present a movable contact supportingsurface in each of the compartments, a movable contact assemblyresiliently supported by the bight portion on each of the movablecontact supporting surfaces, said movable contact assemblies each beingarranged to resiliently engage the stationary contact in thecompartments when the armature is at the energized position and thebight portion is at the contact closing position, and a pair of shockabsorbers positioned on the rear wall of the bight portion to becompressed between the bight portion and the mounting plate when thecontact carrier is moved in said direction beyond the contact closingposition and to be relaxed when the bight portion is at the contactclosing position.

2. The switch assembly as recited in claim 1 wherein the rear surface ofthe bight portion includes a pair of spaced bores each including one ofthe shock absorbers for positioning the shock absorbers on the rearsurface of the bight portion.

3. The switch assembly as recited in claim 2 wherein the shock absorbershave a cylindrical shape.

4. The switch assembly as recited inclaim 1 wherein each of the movablecontact assemblies includes a spring that is compressed to have onelength when the bight portion is at the contact closing position and thearmature is at the energized position and the shock absorbers extendfrom the rear surface of the bight portion a distance sufiicient so thatthe shock absorbers engage the mounting plate and are compressed whenthe springs are compressed to have a length shorter than the said onelength and are relaxed when the springs are compressed to have a lengthequal to the said one length to reduce the bounce of the movablecontacts on the stationary contacts during the movement of the armatureto the energized position.

5. The switch assembly as recited in claim 4 including a pair of springsreacting between the rear surface and the mounting plate for constantlyopposing the movement of the bight portion toward the mounting plate.

6. The switch assembly as recited in claim 1 wherein each of the shockabsorbers is formed as a cylinder of butyl rubber material.

7. The switch assembly as recited in claim 6 wherein each of the shockabsorbers has a bore extending therethrough.

8. The switch assembly as recited in claim 7 wherein each movablecontact assembly includes a portion that is received in a bore in thebight portion which acts as a shock absorbing air piston in the bore tofurther reduce the contact bounce of the switch assembly.

9. In an electromagnetically operated switch, the combinationcomprising: an insulating base providing a row of compartments that areelectrically isolated from each other, a pair of stationary contacts ineach of said compartments with the contacts of each pair spaced onopposite sides of a plane defined by a center line through the base, anelectromagnet having an armature movable from a de-energized position toan energized position when the electromagnet is energized, a movablecontact carrier having a portion operatively connected to the armatureand a plurality of contact support portions movable in the plane in onedirection from a retracted position to an operative position in responseto the movement of the armature from the de-energized position to theenergized position, a movable contact assembly resiliently supported byeach of the contact support portions to resiliently engage thestationary contacts in each compartment when contact support portionsare at the operative position, and at least one elastomeric shockabsorber carried by the movable contact carrier to be compressed whenthe contact support portions are moved in the said one direction beyondthe operative position and to be relaxed when the contact supportportions are at the operative position.

10. The switch assembly as recited in claim 9 wherein the shock absorberis formed of butyl rubber and each of the movable contact assembliesincludes a spring that is compressed to have one length When the contactsupport portions are at the operative position and the shock absorbersextend from the carrier a distance sufficient so that the shockabsorbers engage portions of the base and are compressed when thesprings are compressed to have a length shorter than the said one lengthand are relaxed when the springs are compressed to have a length equalto the said one length to reduce the bounce of the movable contactassemblies on the stationary contacts during the movement of thearmature to the energized position.

References Cited UNITED STATES PATENTS 2,531,025 11/1950 Bradley 335l932,946,872 7/1960 Siebers 335--193 3,196,231 7/1965 Meyer 3351933,354,415 11/1967 Gribble 335132 FOREIGN PATENTS 731,713 6/1955 GreatBritain 335193 HAROLD BROOME, Primary Examiner 3 3". UNITED STATESPrkTENTpFFICE CERTIFICATE OF CORRECTION Patent No. 3,55 Dated December97 Ioventofls) James Stallman It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

C01. t, line A,- cancel "extends" and insert -extend- C01. 5, line 19,cancel "has and insert --have-.

001. 6, line 38, cancel "No. 8Mh034" and insert "No. 8 4 502 Signed andsealed this 27th day of April 1971.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, J'R. Attesting OfficerCommissioner of Patents

